The invention relates to charging in a telecommunications network and particularly to real-time charging of prepaid services.
The GPRS (General Packet Radio Service) is a new service in the GSM system and one of the objects of the standardization work in the GSM phase 2+ at the ETSI (European Telecommunication Standard Institute). The GPRS operational environment comprises one or more subnetwork service areas interconnected by a GPRS Backbone Network. A subnetwork comprises a number of packet data service nodes, referred to as GPRS support nodes, each of which is connected to the GSM mobile network in such a way that it can provide a packet service for mobile data terminals via several base stations, i.e. cells. The intermediate mobile communications network provides circuit-switched or packet-switched data transmission between a support node and mobile data terminals. Different subnetworks are in turn connected to an external data network, to a public switched packet data network PSPDN, for example. The GPRS service thus allows packet data transmission to be provided between mobile data terminals and external data networks, with the GSM network serving as an access network.
In the GPRS system, charging is based on a plural number of charging records CDR generated at the support nodes, the records being transmitted to a charging gateway functionality CGF. From the data it receives, the charging gateway functionality filters the charging data and transmits the filtered charging records CDR to a billing system that generates the actual charging data. A problem with the above described arrangement is that the generating of the charging data is relatively slow. In particular, when a subscriber uses what are known as prepaid services, charging should take place substantially in real-time to avoid a situation where the subscriber could continue to use the prepaid service even though the amount paid in advance by the subscriber had already been exhausted. One solution to the problem is to send the filtered charging data directly from the charging gateway functionality to the billing unit. The term xe2x80x98billing unitxe2x80x99 in this context refers generally to a functional unit that maintains the subscriber""s charging data, or account data, and also comprises, for example, information about the advance payments made by the subscriber for the prepaid services. Alternatively, also data about the GPRS context events could be sent from the support nodes to the billing unit, charging being then based on the context events. In the above cases, problems arise, on one hand, from the complexity and amount of data received from the support nodes and, on the-other hand, from network-specific charging methods that may differ from one another. Charging can be based, for example, on the duration of the service, on the amount of data to be transferred, or on other similar criteria. If the subscriber uses a foreign network, the billing unit must know the charging algorithms of the network concerned; this renders the billing unit configuration complex. Similar problems can also arise in a circuit-switched network, such as the GSM network, and in broadband networks. In the GSM system, for example, different events taking place during a call can have a different impact on charging, depending on the operator, or they may have no impact at all. Such events include quality of service changes, transmission rate changes, location changes, temporary entry into a shadow region, temporary cutting off of the subscriber connection, and changes during an ongoing call in the services used.
An object of the invention is therefore to provide a method and a system implementing the method in such a way that the above problems can be solved. The objects of the inventions are achieved with a method and system characterized by what is stated in the independent claims 1 and 11. The preferred embodiments of the invention are disclosed in the dependent claims.
The invention is based on the idea of providing telecommunications network nodes with a function that converts event data or charging data received from the nodes, by applying the network charging algorithms, to provide a real-time, unambiguous charging data format understandable to the subscriber""s billing unit, expressed as an amount of money spent or as charging pulses, for example. A node in this context refers to a network element, such as a packet network support node GSN or a mobile services switching centre MSC, that provides event data having an impact on charging. Unambiguity means that the charging data are structurally identical in the different telecommunications networks, irrespective of the internal charging algorithms of the networks. The unambiguous charging data are further transmitted to the subscriber""s billing unit that maintains in real-time the subscriber""s charging data. The function associated with the network nodes can also negotiate with the subscriber""s billing unit about charging; for example, the billing unit provides a predetermined amount of the prepaid sum for use to the function associated with the nodes of the network used and when the amount is exhausted, the function can request an additional payment for use.
The method and system of the invention provide the advantage that the subscriber""s charging data can be updated in a real-time process, thus allowing prepaid services to be used. In addition, the invention allows this irrespective of the network used, the charging data of a visiting subscriber thus being also updated substantially in real-time in the home network or a subscriber identity module, for example. The billing unit only needs to know one common charging data structure; each function integrated into the support nodes of a telecommunications network knows the corresponding charging algorithm of the network. Another advantage of the invention is the possibility to optimize the amount of signalling related to the charging data because data on all separate events having an impact on the call rate do not need to be transmitted all the way to the billing unit.